1. Field of Invention
The present invention relates generally to the field of infrared detecting devices and more particularly to the automatic standardized calibration of infrared detection devices.
2. Technical Background
Various methods have been employed to electronically control water flow through a water control device such as a faucet or spigot. Among the accepted and conventional methods is the use of an optical sensor for detecting reflections from an infrared (xe2x80x9cIRxe2x80x9d) source or IR emitter. When processing electronics determine the reflection has exceeded a threshold value, a control signal opens a solenoid valve. Generally speaking, a pulsed IR beam is reflected from an object (such as a user""s hands) and sensed to determine whether to activate or deactivate a solenoid valve to control water flow from the water control device. Pulsed IR sensing remains at the forefront of sensing techniques used with these types of devices due in part to its reasonable performance and low cost.
Because of variations in processing circuits, emitter characteristics and sensor characteristics, it is necessary to calibrate the IR system. Calibration of infrared sensing devices such as, for example, automatically activated flow control devices is labor intensive and inefficient with respect to devices presently on the market. The lost cost IR sensing devices employed in automatically activated flow control devices vary with respect to power requirements, performance, and other criteria. As a result, readings taken by these IR sensing units (such as whether a user""s hands are present beneath the aerator of a faucet) are generally non-uniform from device to device, and therefore often result in improper activation and deactivation of some devices. Similarly, as battery power for these devices decreases over time, so does the power output of the IR sensing devices. Moreover, water droplets sprayed or otherwise deposited on or near the IR detector lens or lens cover have been known to cause such devices to malfunction. As a result, manual calibration of conventional infrared sensing systems of automatically activated flow control devices is generally required during initial installation, and thereafter on a frequent basis following extended periods of use.
Most infrared sensing units have an IR emitter and IR detector embedded in an electronics board in the collar of a faucet. During manufacturing, each emitter and detector has to be screened, requiring technicians to manually adjust settings when they go through calibration steps. A technician is required to make measurements and adjustments to the main electronics board which is time consuming and costly.
The present invention provides a method for calibrating infrared detecting devices which detect the presence of an object by detecting an IR reflection. The output of the IR detector is calibrated by a control module which receives the output of the IR detector and regulates the output of the IR emitter. A single standard pair of an IR detector and an IR emitter is sufficient to calibrate an unlimited number of control modules. The method eliminates the need to manually calibrate and adjust each IR detector and IR emitter that is part of the infrared detecting device. The method uses a standard IR detector and IR emitter with output characteristics in the middle of a suitable operating range. The control module activates the IR emitter with an input value to emit IR radiation which is reflected from a standard object at a standard distance from the IR emitter to an IR detector which is also a standard distance from the object. The output from the IR detector is transmitted to a control module. If the IR detector output is out of the desired range, a calibration manager directs the signal processor to increase or decrease the output of the IR emitter. This process is repeated until the output of the IR detector is within midrange. The value of the corresponding input to the IR emitter to achieve this midrange output value of the IR detector is stored in the nonvolatile memory of the control module and the calibration manager reprograms itself to use this calibration value of input to the IR emitter as a reference standard.